The present invention relates to a method for calibrating the output of a pressure transducer utilizing a differential transformer and particularly to a method in which d.c. voltage of a pressure transducer is forcibly deviated from a reference value corresponding to a reference pressure and thereafter a calibrating voltage is added to the deviated d.c. voltage so that the output voltage of the pressure transducer is calibrated to the reference value electrically.
Pressure transducers utilizing a differential transformer have been known well in the field of electrical pressure detection. Such a pressure transducer comprises, in general, a housing forming a pressure chamber, a pressure responsive member movably supported in the presence chamber and a differential transformer associated with the pressure responsive member. The transformer has a primary and secondary windings and a movable core which are arranged in such a manner that the movable core is moved by the pressure responsive member in response to the pressure exerting thereon and the secondary windings produce, with the primary winding being excited periodically, a.c. voltages corresponding to the position of the movable core. An oscillation circuit is connected to the primary winding for exciting purpose and an AC-DC conversion circuit is connected to the secondary windings for AC-DC voltage converting purpose. According to this conventional arrangement, the pressure transducer detects the pressure and produces d.c. output voltage indicative of the detected pressure. It is a matter of course that each pressure transducer must be zero-calibrated to produce correct d.c. output voltage. Zero-calibration for the pressure transducer has been attained, as disclosed in the United States Pat. No. 3,848,180, by mechanically adjusting the position of the pressure responsive member fixed to the movable core. Although this conventional calibrating method is simple, it is difficult to attain fine zero-calibration on the pressure transducer designed to be small in size.